Apparatus for coating metal strips



June 4, H940.

. Ni. G. WHITFIELD ET AL APPARATUS FOR coATING METAL STRIPS Filed Sept.24, 1956 5 Sheets-Sheet l June 4, 1940.,

G. WHITFIELD ET AL.

APPARATUS FOR COATING METAL STRIPS Filed Sept. 24, 1956 3 Sheets-Sheet 2.0m )WNS @M www, mmf/22514,

June 4 1940 M. G. WHITFHELD Er An. 2,203,06

APPARATUS FOR COATING METAL STRIPS Filed Sept, 24, 1936 3 Sheets-Sheet 5A Ul Patented June 4, 1940 PATENT OFFICE APPARATUS FOR. COATING METALSTRIPS Mai-simil c. Whitfield `and Victor Slleshuno,

` Knoxville, Tenn., assignors to Reynolds Metals Company. New YorkDelaware N. Y., a corporation of Application September 24, 1936, SerialNo. 102,433

18 Claims.

This invention relates to apparatus for the metal coating of elongatedstrips, such as wires, bands, sheets. etc., which will be referred tohereinafter generically by the single term ,strips, but it is to beexpressly understood that the term, strip.is intended to embraceelongated material of any suitable width, any, suitable thickness, andany suitable cross section, whether round, rectangular, or otherwise.

While as respects certain features of this invention the apparatusherein disclosed is of utility in coating strips of `various metals witha variety of coating metals, the `invention has particular utility andwill be illustrated by reference to its use in the coating of iron orsteel strips with aluminum.

It has heretofore been proposed to form a ductile strip of aluminumcoated iron or steel by first prepacking the iron or steel strip with asuitable reducing gas and thereafter introducing the prepacked stripinto an aluminum bath below the level of the surface thereofA so as toavoid as far as possible the presence of aluminum oxide at the interfacebetween the base metal and the aluminum, but efforts to apply thismethod in practice have encountered certain practical difficulties whichhave interfered with the efficient practice of this method. It is anobject of this invention to provide apparatus which is simple incharacter and yet both effective and efcient for the carrying out of themethod above identified.

Another object of this invention is to provide an apparatus of the typecharacterized which will assure that the base metal is thoroughlydegl-eased or cleaned of any oily material at the surface i thereof.

Anotherobject of this invention is to provide apparatus of the typecharacterized which will assure that any scale or oxide on the basemetal is loosened and completely removed from the surface thereof.

Another object of this inventionl is to provide apparatus of the typecharacterized which assures that all foreign material is removed fromthe surface of the metal to be coated.

Another object of this invention is to provide apparatus of the typecharacterized with a fur r nace fortreating the base metal with reducinggas in advance of coating the same that may be readily manipulated tofacilitate threading of the strip therethrough and the properpositioning of the exit therefrom with respect to the coating bath.

Another object of this invention is.to provide apparatus of the typecharacterized with a furnace for treating the base metal with reducinggas in advance of coating the same that has improved means forpreventing escape of the gas where the strip is admitted thereto andwhich at the same time will not unduly interfere with the movement ofthe strip into the furnace.

Another object of this invention is to provide apparatus of the typecharacterized wherein the means for delivering the strip to the bath maybe readily moved with respect to the bath so that its exit end may beimmersed in the `bath or withdrawn therefrom.

Another object o1' this invention is to provide apparatus of the typecharacterized with means whereby the temperature of the strip may benicely controlled and predetermined at various positions in its traversethrough the apparatus.

Another. object of this invention is to provide apparatus of the typecharacterized wherein the means for delivering the strip beneath thesurface of the bath is of improved construction and preferably readilyaccessible so that it may be readily opened.

Another object of the present invention is to provide apparatus of thetype characterized with means immersed within the coating bath forguiding the direction of the strip and which is not readily attacked orinterfered with by the metal ofthe bath.

Another object of this invention is to provide apparatus of the typecharacterized with means to prevent the oxide skin on the surface of themetal bath from being drawn onto the moving strip.

Another object of this invention is to provide apparatus of the typecharacterized withmeans for quenching the coated strip as it leaves thebath so as to predetermine the depth of interaction-between the base andcoating metals.

Another object of this invention is to provide apparatus of the typecharacterized with improved means for moving the strip through theapparatus.

Another object of the present invention is to provide apparatus of thetype characterized which is effective and eflcient in enabling the`rapid coating of continuous strips with a substantially uniform layerof coating metal united to the base strip by a substantially uniform andcontinuous alloy bond of predetermined thickness. i

Another object of the present invention is to provide apparatus of thetype characterized which is inexpensive to assemble and install,

which may be readily manipulated by unskilled labor, and which is strongand durable.

Other objects will appear as the description of the invention proceeds.f The invention is capable of receiving a variety of mechanicalexpressions, one of which is shown on the/accompanying drawingspbut itis to be expressly understood that the drawings are for purposes ofillustration only, and are not to be construed as a definition of thelimits of the invention, reference being had to the appended claims forthat purpose.

Referring in detail to the drawings, wherein the same referencecharacters are employed to designate corresponding parts in the severalgures- Figs. 1, la and 1b are complementary views, somewhat diagrammaticin character, illustrating apparatus embodying the present invention,Fig. 1 illustrating one end of the apparatus, Fig. la illustrating theintermediate portion of the apparatus, and Fig. 1b illustrating theopposite end of the apparatus;

Fig. 2 is a fragmentary viewv on an enlarged scale illustrating themechanism for delivering the gas treated strip from the furnace to thecoating bath;

Fig. 3 is a fragmentary view on an enlarged scale illustrating the meansfor effecting a seal at the entrance to the furnace; and

Figs. 4 and 4a show a nozzle with provision for heating the same.

In the'embodiment illustrated the apparatus, which is composed of aplurality of ydevices that may be separately mounted or, if preferred,provided with a common bed plate or support, includes supply means forthe base strip, generally designated A, degreasing apparatus, generallydesignated B, bluing apparatus, generally designated C, picklingapparatus, generally designated D, washing apparatus, generallydesignated E, apparatus for treating the strip with gas, generallydesignated F, coating apparatus, generally designated G, drivemechanism, generally designated H, and take-up means,generallydesignated I. Referring to these several pieces of apparatus inthe order just referred to, because that is the order in which a stripto be coated preferably passes throughv saidV several pieces ofapparatusi The supply means A may be of any suitable character for thelength'and form of the strip to be coated. As shown, a standard Icarries a suitable axle I I by which a reel I2 may be mounted on saidstandard to rotate thereon. In order to impose suitable tension on thestrip I3 to be coated, suitable braking means, as a friction drum, ispreferably associated with said reel, so that the reel may not rotate sorapidly as to enable the strip to become slack as it is drawn off.

From the supply means A the strip passes to degreasing apparatus B toremove all oil or greasy material from the surface of the strip. Saiddegreasing apparatus may be of any suitable character, being shown ascomposed of la pair of plates III and I5, mounted upon a suitablestandard I6 and adjustably spaced by bolts I1 carrying wing nuts I8.Retained between said plates I4 and I5, in the form shown, is cottonWaste I9, which may be compressed by adjustment of the wing nuts so asto engage the strip I3 with the proper pressure. Carried by the plate VIis a suitable receptacle 20 as a tank provided with a perforated bottom,to maintain the cotton waste suitably soaked or saturated with a solventmaterial, such as carbon tetrachloride, that will act upon the greaseand oil and effect the removal thereof. It is to be expresslyunderstood, however, that any other suitable degreasing apparatus may beemployed within the broader aspects of the present invention.

From the degreasing apparatus B thestrip I3 passes to the bluingapparatus C. Experience has n demonstrated that merely applying asolvent to the surface of the base metal is not sufficient to otherwiseseparating from the base metal-ex treme care must be exercised inthoroughly clean-r` ing the surface of the base meal. covered that ifthe base metal is heated so 'as-to form a deep blue oxide on the surfacethereof,

We have dsfollowing the application of a solvent for the oil or greaseand before passing the strip into a picklingbath, the surface of theiron or steel ls so conditioned that the coating metal may adherethereto uniformly throughout its entire surface.

The bluing apparatus C may be of any suitable character for producingthe deep blue oxide on the opposed faces hof the strip. As shown, saidappa-` ratus includes a suitable standard 2I which carries a bank ofburners 22 supplied with gas and y air through pipes 23, which may beprovided with suitable valves 24 for adjusting the iiow and theproportioning of the air and gas. Said burners 22 are positioned closelyadjacent the path of movement of the strip I3, and a cover f not shown)is preferably supplied, so that the strip I3 Vas it passes through thebluing apparatus may be properly raised to a temperature at which thedeep blue oxide forms with relative uniformity over both surfaces of thestrip. The valves 24 enable the flames of the burners to be adjusted soas to effect the desired heating of the strip to attain this end. Theoxide so formed may be easily removed, and with its removal the oil orgrease is entirely removed from the surfaces of the strip. In place of agas heated bluing apparatus, however, any other suitable furnace may beused, as one heated by electricity.

From the bluing apparatus C the strip I3 passes into and through apickling apparatus'D. Said apparatus may be of any suitable size andconstruction, and as shown' takes the form o-f a container 25 holding apickling liquid 26 of any suitable character, an 8% hydrochloric acidsolution having been found suitable. The end ofthe container 25adjacent. the bluing apparatus carries a suitable guide roller 21 overwhich the strip passes into the tank, and interiorly the tank has one ormore guide rollers 28 over which the strip passes in its traverse of thetank. The pickling tank is preferably placed closely adjacent the bluingapparatus so that the strip, when it enters the tank, is still at arelatively high temperature, as it has been discovered that the scale isremoved more easily if the strip enters the pickling liquid while hot.The pickling solution is preferably maintained somewhat below theboiling point to avoid undue evaporation, as around 170 F., and to thisend a steam pipe 0r coil 29 leads into a.aos,eos

the liquid, and is provided with a suitable control valve 3l, so thatthe temperature of the bath may be maintained at the desired degree ofheat. Ii preferred, the flow of steam may be controlled by a thermostatsubjected to the temperature of the bath so that the bath temperaturewill be maintained uniform. The pickling bath is also preferably used toafford one terminal for the electric heating of the strip, so that thetemperature of the strip will be progressively increased as it leavesthe pickling tank until it has passed through the gas treating apparatushereinafter described. As shown, a carbon electrode 3l is disposedwithin the tank and is connected through wire 32 with any suitablesource of electricity. Said electrode is preferably out of contact withthe strip, so that surface contact between the strip and electrode willnot impose an undue drag upon the movement of the strip, the picklingliquid acting as a conductor between the strip and the electrode.

From the pickling apparatus D the strip I3 passes directly to a washingapparatus E of any suitable character. The strip preferably runsdirectly from the pickling tank to the washing apparatus so as tominimize drag on `the strip, and the application of streams of hot andcold water and steam to the strip before the strip has hadan opportunityto dry also facilitates removalof any dirt that the strip may havepicked up from the surface of the` liquid in the pickling apparatus. Asshown, a pair of rotarybrushes 33 engage the strip as it leaves thepickling tank to effect a preliminary removal of the scale and oxidethat has been loosened in the pickling bath, and thence the strip entersahousing 34 mounted on any suitable standard 35 and in which is disposeda suitable roller 36 so that the strip passes in a straight line fromthe outlet of the pickling tank to and through the washing apparatus.Also mounted in the washing apparatus 34 is a `second pair of rotaryscrubbing brushes 31. These rotary brushes, 33 and 31, preferably rotatein a direction so that the friction exerted thereby on the strip I3tends to feed the strip in its direction of normal traverse, therebymaintaining the strip under proper tension and facilitating its forwardmovement, but said brushes preferably rotate at a `peripheral speedwhich is materially greater than the linear speed of the strip I3 sothat there is a substantial relative movement between the brushes andstrip to effect the desired scrubbing action thereon. Said brushes 31are preceded and succeeded by a suitable number of jets of water, 38 and39, which may be either cold water or hot water or both, said jetsbeingdisposed so as to spray the water directly upon the two faces of thestrip both in advance of the action of scrubbing brushes 31and after thestrip has passed through said brushes so that the action of said jets,when taken in conjunction with the action of said brushes, is to loosenand remove any foreign material such as scale, oxide, dirt, etc. that isstill adhering to the strip, to the end that a perfectly clean strip ofiron or steel is obtained. The washing apparatus is also preferablyprovided with steam jets 40 coacting with both faces of the strip fordirecting high pressure steam directly against the faces of said stripto assist in heating and drying it before it reaches thefurnace F.

From the washing apparatus the strip I3 passes 4directly into thefurnace for treating the strip with a suitable reducing gas. As hereshown,

any suitable size, construction and material and lined with a suitablerefractory 42 so as to render it gas-tight. The furnace is shown asmounted approximately midway of its length on a supporting member 43having attached thereto a curved or other suitable rocking surfacedelement 44 in engagement with the support 45. Said` furnace adjacent itsoutlet end is provided with legs or other suitable supports 46,preferably of such length that they will engage the support 45 when thefurnace is in its normal position as illustrated on the drawings, whilethe entrance end of said furnace is provided with legs or other suitablesupports 41 which are materially shorter than said legs 46 and which aredesigned to be engaged with blocks 48 or other suitable elements whenthe furnace is in its normal position. When blocks 48 are removed thefurnace may be rocked as a whole on its rocking element 44 soas to tiltthe outlet end of the furnace with respect to'the metal coating bath,for a purpose that will appear hereinafter.

The strip I3 enters the gas-containing chamber 49 through a slot oraperture 50. In order that leakage of vgas shall be minimized and at thesame time in order that there shall be'a minimum opposition to movementof the strip due'to the presence cf the sealing means, said entrance ispreferably provided with a sealing means such as is more particularlyillustrated in Fig. 3. As here shown, the strip is made to pass betweensurfaces of metal foil pressed into yielding contact with the movingstrip, said metal foil being preferably pressed into contact withopposed faces of the strip at more than one point in the length of itstraverse through the sealing means.' As shown, two opposed sets ofsealing surfaces are provided, each sealing surface being formed of aplurality of sheets of metal foil 5I, preferably copper foil, backed upby crumpled metal foil 52, preferably aluminum foil, the latter foil inturn being backed by asbestos 53, which may be provided in a loose massor in the form of sheets or blocks. In engagement with the asbestos is aplate or block 54 of any suitable material that is acted on by a thumbscrew 55 having its threads engaged in a nut suitably provided in thecover of the sealing unit and projecting to the exterior of the unitwhere said thumb screw may be rotated to impose the desired degree ofpressure on the opposed sets of foil surfaces 5I in contact with 4themoving strip I3. `Experience has demonstrated that a seal formed bymetal surfaces as described keeps the strip clean, does not scratch thesurface of the strip, and effectively cuts down the leakage of gas to aminimum, while the frictional opposition to movement of the stripimposed thereby is kept within reasonable limits. The metallic parts ofthe seal are suitably insulated so as `to prevent short circuiting ofthe strip which is being heated by current flowing therethrough ashereinafter explained.

At its outlet end the furnace F carries an extension 58 in which ismounted a roller 51 on a shaft 58. The preferred details of constructionat the outlet end of the furnace are illustrated in the enlarged view ofFig. 2. As here shown, the roller 51 conveniently takes the form of apiece of tubing provided with ends suitably apertured for mounting onthe shaft 58, so that the roller is hollow in order that cooling watermay be passed through the same, the cooling water being admitted anddischarged through suitable openings 58' in the shaft 58 and pipesleading to and from the same. Roller 51 or shaft 58 also serves as thecontact fora brush or electrode 59 connected by main 6I) with a sourceof electric current as hereinbefore referred to, so that electricity mayflow toand through the strip I3, to the outlet electrode 3I heretoforedescribed in the piclcling apparatus, and thereby said strip, owing ,toits inherent resistance, is suitably heated throughout its traversethrough the furnace F to facilitate the elimination of any oxygenadhering to the strip yand also to facilitate the pretreatment of thestrip with the reducing gas which constitutes the atmosphere inl saidfurnace. It `will be understood that the support for'the shaft 58 isA'suitably insulated so as to prevent short circuiting of the currentdesigned to flow through the strip I3, as are also the roller 36 andother metallic elements contacting the strip between the electrodes 3land 59. Extension 56 is preferably provided with a safety cover 6I whichmakes a sealed contact with said extension 56, asby a seal employing alow fusing metal as indicated at 62, so that in the event of anexplosion in the hydrogen or other gas in the furnace F said lcover maybe blown off without damage to the furnace. Extension 56 is also shownas provided with a sight tube 63 closed by a suitable transparent windowso that the condition of the strip'in the furnace may be observed.

Projecting from the extension 56 (see particularly Fig. 2) is a tube 64which provides a tubular extension of the furnace chamber and throughwhich the strip I3 is designed to pass after it leaves the roller 51.Attached to the end of the tube 6471s a nozzle 65 which provi-des arestricted outlet 66 that is little larger than the cross section of thestrip being acted upon. Projecting laterally from the tube 64 is a lug61 on which is pivotally mounted a lever 68 carrying at its end a roller68 which is designed to be immersed in the molten metal of the coatingbath and over which the strip I3 is made to pass as it traverses saidbath. Lever 68 is preferably made adjustable so that the roller 69 maybe suitably located with respect to the outlet orifice 66, and to this;end lever 68 has a laterally extending apertured lug 10 which cooperateswith a threaded stem 1I carrying lock nuts 12 and suitably mounted onthe wall of the tube 64. Lock nuts 12 enable the lever to .be locked inits adjustedl posi-tion. A

sight tube 13 closed by a transparent window of any suitable characteris also preferably positioned in the wall of the tube 64 adjacent thenozzle 65 so that, the condition of the strip passing through the tube64 can be observed. Tube 64 may also be provided with the inlet pipe 14for the gas of the furnace F, and an outlet pipe for said gas may beprovided at 15 as shown in Fig. 1a.

Thus it will be seen that the strip I3 may be passed through the furnaceF and simultaneously heated by a current of electricity traversing saidstrip from the electrode 59 to the electrode 3I- although if preferredthe strip may be suitably' means maybe employed for controlling thecurrent inlet through the' electrodev 59 `so as to maintain the desiredtemperature, and this means may be automatically controlled sothat asubstantially uniform temperature of the strip is maintained.' "i

If the furnace F be heatedby gas rather than by using the stri-p itselfas an electrical resistance element, the roller 51 need not ordinarilybe water cooled, but water cooling may be employed if desired; the watercooled roller being of particular utility in controlling the temperatureof thestrip to facilitate the cooling thereof to a temperatureapproximating, or somewhat below that of the coating bathwhere such isfound to be-desirable as in thecase 'of coating iron or steel stripswith aluminum. To assure the desired cooling of the strip before itenters the coating bath, the tube 64 may also be suitably Water cooledin whole or in part so as to'secure a predetermined temperature of thestrip when it reaches the outlet 66 of the nozzleV 65,.

Disposed adjacent the outlet end of the furnace F, and in a position ,sothat the outlet 66 of the nozzle 65 may be'immersed in the molten metal,is the coating apparatus G. As here shown, a furnace 16 of any suitablesize, construction and character has mounted therein a melting pot 11which may be heated in any suitable way, as .by an electric resistorelement 16. The surface of the .bath is indicated at 19, and thetemperature of the bath may be controlled by use of any suitablethermostatic or thermoelectric mechanism subjected to the temperature ofthe bath 'and connected to suitable control Aswitches in circuit withthe resistor 18. As shown,

a contact electrode v8l! is immersed in thebath and connected to themain through Wire 8|. 'I'he bath itself constitutes a conductor path tocomplete the heating circuit, and wire 8l may be connected with anysuitablerheostat for varying the temperature of the strip, eitherautomatically or manually. As shown in Fig. 1b, the outlet of the nozzle65 is normally disposed below the surface of the bath so that the stripI3 may .pass directly from the reducing atmosphere in the furnace andits extension into contact with the molten metal of the bath withoutpreliminary contact with the air an-d without having to traverse more ofthe surface of the molten metal in the bath than is dened by the crosssection of the passage in -Whether to thread the strip through theapparatus or to clean out the nozzle if it .becomes caked with coatingmetal', etc. To further facilitate threading, cleaning of the'nozzle,etc., nozzle 65 is preferably made in two parts separable on a planeextending lengthwise of the passage therethrough and secured together inany suitable way so that the upper part of the nozzle maybe removedvvith respect to the lower par-t to com, pletely expose the passagetherethrough.

The roller 69 immersed in the molten metal of the bath must be ofspecial construction so as to ythe furnace extension or nozzle which, asbefore l enable it to function satisfactorily in the presence of moltenmetal. In conformity with the present invention a single roller ispreferably employed in the molten bath, and as heated aluminum is muchmore active than other coating metals ordinarily used, said roller toprevent its sticking to its shaft or other mounting means is providedwth graphite bearings. Preferably, as

shown in Fig. 2, said roller is mounted on two graphite sleeves 82 so asto give a graphite-tographite contact and a double lpossibility ofrelative movement. The surface of the roller 69 is preferably crowned tofacilitate its holding of the strip in ltscentral guided position.

From the coating bath G the strip 23 is passed over a roller 84preferably suspended from the ceiling or other elevated support, so thatthe reach of the strip I3 as it leaves the coating bath is vertical orsteeply inclined. `Immediately after the strip leaves the surface 'I9 ofthe coating bath it is preferably subjected to the action of a suitablequenching means, here shown as a plurality of quenching sprays 85 whichoperate on both sides of the strip I3 and which may use compressed air,water, water atomized by compressed air, or any other suitable coolingmedium to promptly chill thc strip and thereby limit the extent ofinteraction between the coating metal and the strip. For particulartypes of coating itis also desirable to provide means where the strip I3leaves the metal bath to prevent the oxide film on the surface of themolten metal being drawn up onto the surface of the moving strip. Whensuch is desirable, a pair of metal strips or plates may be partlyimmersed in the molten metal and provide an exit slot therebetween, said4exit slot exceeding the thickness of the strip by a substantial amountso as not to wipe any of the coating metal from the strip while actingat the same time to dam back the surface of the molten metal and preventits unrestricted flow to and into contact with the moving strip.Experience has demonstrated that the use of an exit orifice of thischaracter also tends to increase the thickness of the coating obtained.

From the roller 84 the strip I3 moves to driving mechanism H of anysuitable character. As here shown, said driving mechanism consists4 of aplurality of rollers, three being shown and designated 86, 8'I and 88,which have interconnected driving mechanism (not shown), and which aremounted upon a suitable standard 89. One of said rollers, as 86, isshown as having a direct drive through a belt 8U froman electric motor9|, although any other source of power for driving said rollers 86, 81,88 may be employed. By preference variable speed drive mechanism isassociated with said motor 9| so that the speed of the drive rolls maybe adjusted to maintain the proper value. The strip I3 passes under theroller 86, over the roller 81 and under the roller 88, these rollersbeing spaced by an ample clearance, say from 2 to 3 inches, so that thestrip is not compressed between the same and the drive of the strip iseffected only by the action of friction on one side of the strip.Driving mechanism of this character can handle all types of coatings anda wide variety of coating thicknesses. At the same time if in startingthe apparatus any lumps of metal adhere to the strip as a result of itspassing through an incompletely molten bath, no undue strain is imposedon strip I3 as would be the case if its feed were effected by pinchingrolls. In the structure illustrated, the drive is effected by frictionand only a predetermined small tension is maintained on the strip I3 tohold it rmly in contact with the arcuate surfacesof the three rollersaround which it passes.

` From the drive mechanism H the strip I3 passes to the take-upmechanism I, which may be of any suitable constructiony As shown, a reel92 is suitably mounted on a standard 93 and has a suitable frictiondrive, as by belt 94, from any suitable source of power, as an electricmotor driven shaft 95. Said take-up mechanism is preferably adjustableso that the friction therein assures au even and predetermined tensionon the strip I3 to the end that said strip is properly maintained indriving engagement with the rolls 8B, 8l and 88 as herein referred to.

The operation of the apparatus will now be apparent from the foregoingdetailed `description of the componentv parts thereof. In general, thestrip I3 is drawn off of the reel I2, passed frictionally in contactwith the waste I9 that is soaked with a suitable solvent for the oil andgrease, subjected to the heat of the furnace at C so as to produce agenerally uniform deep blue oxide over both faces thereof, and thenpassed through the pickling tank and the scrubbing and washingapparatus, whereby all scale, dirt, grease, oil, oxide, etc., arethoroughly loosened and removed, leaving the strip completely cleaned atboth surfaces thereof.

While in the pickling tank the strip is subjected to the electrode 3|and its temperature progressively increased by contact of high pressuresteam therewith as it passes through vthe washing apparatus so that thestrip is also thoroughly dry before/entering the reducing atmosphere ofthe furnace F. Strip I3 passes between the rubbing metal surfaces of thesealing apparatus at the inlet of said furnace F and traverses thereducing atmosphere of said furnace to the roller 5l, during which timethe temperature of the strip is progressively increased to thattemperature desirable for the pretreatment of the strip with thereducing gas. From the roller 5l the strip, still in thereducingatmosphere, passes through the tube 64 and nozzle 65 to apoint`within` the `bath of molten metal which is below the surfacethereof, so that the strip has contact neither with the air nor with anysubstantial amount of oxide lm on the surface of the molten material,but while in a suitably pretreated condition due to its passage throughthe reducing atmosphere and its heating to a relatively hightemperature, which is preferably on the order of 1350 F. or higher foriron or steel pretreated with hydrogen and to be coated with aluminum,it is passed directly into contact with the molten coating metal underconditions which will minimize oxide formation between the base stripand the coating metal. During this passage from the furnace to themolten metal the base metal is preferably reduced in temperature to atemperature approximating or somewhat lower thanthe temperature of themolten aluminum, say on the order of 940 F. to 1,000 F. This cooling maybe controlled by the water cooling of the roller 51, the tube 64, or inany other suitable way, so as to assure that the strip I3 has thedesired temperature when it reaches the outlet 86 of the nozzle 85. Fromthe coating bath the metal passes immediately to the quenchbe coatedenters the aluminum bath may be of the type hereinbeiore described, itis sometimes desii-able to heat the nozzle other than' from the heat ofthe bath, because, particularly when coating relatively large strips orwhere the volume of metal passing through the bath is relatively large.sufficient heat is not supplied from the bath to keep the nozzleproperly heated and also provide the requisite amount of heat forabsorption by the metal to be coated. This may result in the bathfreezing up or the nozzle becoming clogged with resultant sticking ofthe strip therein. By heating the nozzle from an extraneous source ofheat it may be maintained at the appropriate temperature and. assist inbringing the strip to the proper temperature, abstracting little or noheat from the bath and thereby avoiding interference with the properoperation thereof.- Moreover, the use of heating means associated withthe nozzle permits the use of a lower average bath temperature andcloser control thereof, which in turn enables a more ductile coating tobe formed. Therefore, the provision for heating the nozzle may be usedto facilitate the securing of a ductile coating even when such heatingmeans is not required by reason of the mass of metal being passedthrough the bath.

The nozzle may be heated in any suitable way. As shown in Figs. 4 and4a, the nozzle 96 has associated therewith suitable electric heatingelements, here shown as resistance elements 91 suitably embedded ininsulating cement 98 and disposed in the channels or grooves 99 formed lin the wall of the nozzle. The electric resistance elements areYconnected in circuit in any suitable way with an appropriate source ofcurrent and any suitable thermostatic means as a thermocouplediagrammatically illustratedat |00 may be associated with the heatednozzle and the source of current so as to regulate the current suppliedto the end that the desired temperature may be maintained withsubstantial uniformity.

Experience has demonstrated that apparatus as hereinbefore described maybe satisfactorily and efficiently used in the coating'of iron and steelstrips, wire, etc., with aluminum so as to produce a uniformly adherentcoating of aluminum on the iron or steel, said coating being ofsubstantially uniform and predetermined thickness, and the resultantproduct being ductile and capable of being bent, drawn, rolled, and

.subjected to other coldworking operations without danger of thealuminum coating being stripped, peeled or otherwise detached from thebase strip. Depending upon the size of the strip and the thickness ofthe aluminum coating desired, speeds from ten to twenty-five feet perminute have been satisfactorily used, it being understood that the speedof traverse as well as the temperatures employed will vary with theform, size and material of the base metal, the character of the coatingmetal, the thickness of coating metal desired, the thickness of alloybond therebetween to be obtained, etc. The present apparatus providesfor ready adjustment of the various temperatures employed, and thereforethe apparatus of the present invention is particularly flexible inpermitting the coating of strips, wires, etc. of various sizes, crosssections and materials with various coating metals, obtaining varyingthicknesses of coating and bond, by suitably controlling the speeds,temperatures, and other factors hereinbeore I@- ceiving a variety ofmechanical expressions, someof which will now readily suggest themselvesto those skilled in the art, while changes may be made in the details ofconstruction, arrangement, proportion, material, etc., and certainfeatures used without other features, without departing from the spiritof this invention. Various forms of drive mechanism, take-up mechanism,furnaces, baths, pickling apparatus, cleaning apparatus, heatingapparatus, drying apparatus, cooling apparatus, etc., may be usedwithout departing from the present invention provided they are suitablefor carrying into effect the operations and obtaining the results hereinset forth. Reference is 'therefore to be had to the appended claims fora definition of the invention.

What is claimed is: y

1. In an apparatus for coating a strip of metal with a coating metal, incombination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, means forthoroughly cleaning said strip in advance of treatment of said strip bya reducing gas including degreasing means and heating means adapted toform a blue oxide layer on said strip after it has passed through saiddegreasing means, and a furnace in which the cleaned strip is thereafterpretreated with a reducing gas prior to entering into said bath.

2. In an apparatus for coating a strip of metal with a .coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed` by said drive mechanism, means forthoroughly cleaning said strip in advance of treatment of said stripwith reducing gas including means for heating said strip to form a blueoxide layer thereon, means for thereafter removing said oxide from saidstrip, and a furnace in which the cleaned strip is pretreated with areducing gas before entering-intogsaid bath.

3. In an apparatus for coating a strip of metal with a coating metal, incombination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, means forthoroughly cleaning said strip in advance of treatment of said stripwith reducing gas including means for heating said strip to form a blueoxide layer thereon, a pick-v ling bath through which said strip isthereafter passed while said strip is still hot, and a' furnace in whichsaid cleanedV strip is pretreated with a reducing gas before enteringinto said bath.

4. In an apparatus for coating a strip of metal with a coating metal, incombination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, meansfor'thoroughly cleaning said strip in advance of treatment of said stripwith reducing gas including means for `heating said strip to form a blueoxide layer thereon, a picklng bath into which said strip is passedwhile it is still hot, means for scrubbing and washing said strip as itleaves said pickling bath, and a furnace in which the cleaned strip isthereafter pretreated with a reducing gas before entering into saidbath.

5. In an apparatus for coating a strip of metal with a coating metal, incombination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, means forthoroughly cleaning said strip of grease. oxide and scale, means forthereafter pretreating said strip with a reducing gas including anelongated furnace through which said strip is passed on its way to saidbath, and means for mounting said furnace whereby it may be tilted aboutan axis transverse to its length to` move the exit of said furnace withrespect to said bath.

6. In an apparatus for coating a strip of metal with a coating metal ofthe type embodying a furnace wherein the strip is pretreated with areducing gas prior to its passage through a coating bath, means forsealing the entrance into said furnace through which said strip passesincluding packs of metal foil pressed into scaling contact with opposedfaces of said strip.

7. In an apparatus for coating a strip of metal with a coating metal, incombination with drive mechanism for the strip and a coating bath`through which said strip is passed by said drive mechanism, a furnacecontainingl a reducing gas through which said strip is passed on its wayto said bath, said furnace including an outlet adapted to be immersed inthe metal of said bath, and means mounting said furnace whereby it maybe tilted about a transverse axis to raise and lower said outlet withrespect to said bath.

8. In an apparatus for coating a strip of metal with a coating metal, incombination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, a furnacecontaining a reducing gas through which said strip is passed on its wayto said bath, said furnace including an outlet adapted to be immersed inthe metal of said bath, and

`means mounting said furnace whereby it may be tilted about a transverseaxis to raise and lower said outlet with respect to said bath, saidmeans including a rocking support for said fur- 4 with a coating metal,in combination with drive mechanism, a furnace containing a reducing gasthrough which said strip is passed on its wayto said bath, said furnaceincluding an outlet adapted to be immersed in the metal of said bath,and means mounting said furnace whereby it may be tilted about atransverse axis to raise and lower said outlet with respect to saidbath, said means including a rocking support `for said furnaceintermediate the length thereof, and supports of unequal length at theopposite ends of said furnace whereby the shorter of said last namedsupports may be blocked to retain said furnace in normal position orunblocked to permit tilting of the furnace about said transverse axis.

l0. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, a furnacecontaining a reducing gas through which said strip is passed on its wayto said bath, means in said furnace for progressively heating said stripas it passes through said furnace, an extension on said furnace throughwhich said strip passes into said bath at a point below the level of thesurface thereof, and means associated with said extension for coolingsaid strip therein.

11. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, a furnacecontaining a reducing gas through which said strip is passed on its wayto said bath and means for retaining said strip in contact with saidreducing gas until it enters said bath, said means including a tubularextension through which said strip passes, said extension dipping intothe molten metal of said bath, and means carried lby said tubularextension and disposed in said bath for guiding the movement of saidstrip.

l2. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough .which said strip is passed by said drive mechanism,a furnacecontaining a reducing gas through which said strip is passed on its Wayto said bath and means for retaining said strip in contact with saidreducing gas until it enters said bath, said means including a tubularextension through which said strip passes, said extension dipping intothe molten metal of said bath, and means carried by said tubularextension and disposed in said bath for guiding the movement of saidstrip, said means including a roller and a bearing `therefor includingcooperating graphite sleeves whereby said roller may rotate freelywithin said molten metal.

13. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, a furnace inwhich said strip is pretreated with a reducing gas on its Way to saidbath, means for retaining said strip in contact with said reducing gasuntil it enters said bath, and means disposed above and closely adjacentthe surface of said bath for quenching said strip immediately after itleaves said bath.

14. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, a furnace inwhich said strip is pretreated with a reducing gas on its way to saidbath, means` for heating said strip as it passes through said furnace,means for retaining said strip in contact with said reducing gas untilit enters said bath, and means disposed above and closely adjacent thesurface of said bath for quenching said strip immediately after itleaves said bath.

15. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed byvsaid drive mechanism, a furnace inwhich said strip is heated on its way to said bath, means for coolingsaid strip `between said furnace and said bath but without contact withthe air, and means for quickly quenching said strip as it leaves saidbath.

16.. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a. coating baththrough which said strip is passed by said drive mechanism, a furnacethrough which said strip passes on its way to said bath, means forheating said strip as it passes through said furnace, and means forcooling .said strip between said furnace and said bathk but withoutcontact with the air.

17. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a. coating baththrough which said strip is passed by said drive mechanism, a furnacehaving a nozzle projecting into the metal of said bath and through whichsaid strip is introduced into the metal of the bath, and a heatingelement associated with said nozzle for predeterminately heating thestrip passing therethrough.

18. In an apparatus for coating a strip of metal with a coating metal,in combination with drive mechanism for the strip and a coating baththrough which said strip is passed by said drive mechanism, a furnacehaving a nozzle projecting into the metal of said bath and through whichsaid strip is introduced into the metal of the bath, a heating elementassociated with said noz'- zle for predeterminatcly heating the strippassing therethrough. and thermostatic means subjected to thetemperature rat said nozzle for regulating said heating element.

MARSHALL G. WHITFIELD. VICTOR sHEsHUNoFF.

